1. Field of the Invention
This invention relates to a fluid control device, in particular a non-return valve arrangement in a packaging machine.
2. Description of the Prior Art
In liquid packaging machines it is conventional to have dosing fillers containing non-return valves which control the liquid flow through the fillers to the packaging containers. These valves are spring-biassed into their closed positions and are forced open by the liquid as it is pumped stepwise towards the containers. For example, EP0090664A discloses a liquid packaging machine in which the dosing filler comprises upper and lower bellows tubes co-axial with each other and with a first, spring-biassed, non-return valve by way of which the upper bellows tube communicates with the lower bellows tube. The lower bellows tube communicates with a filling nozzle arranged co-axially beneath it and containing a second spring-biassed, non-return valve.
The liquid is pumped through the filler by vertical reciprocation of the first non-return valve.
To sterilize such a filler internally, it is conventional to pump a sterilizing liquid therethrough in the same manner as the filling liquid is pumped therethrough. However, sterilizing liquid residues may remain in the filler and need flushing out before filling can commence. The flushing medium can be steam, in which case the filler becomes full of gaseous matter. To remove the gaseous matter, the product can be pumped through the filler, in which case the product may not be re-usable and the process of removal takes some time.
It may be preferable to employ steam for sterilization, rather than to employ a sterilizing liquid, because any steam residues are simply pure water, but again the filler becomes full of gaseous matter.
Magnetic operation of fluid control valves is well known, as can be seen from, for example, U.S. Pat. Nos. 2,589,188; 3,652,054: 4,349,042; 3,774,878: DE2234972A; DE3515848 and FR1106163.
The movable closure member of the valve comprises soft or hard magnetic material, or is connected to another member which is of soft or hard magnetic material. Disposed externally of the valve housing is either a permanent magnet movable between an active position in which it controls the closure member and an inactive position, or an electromagnet energisible to control the closure member. FR1106163 and DE 2234972A both discloses non-return valves biassed closed by springs and with electromagnets energisible to open the valve closure members.